Polarity Of Medium Research Articles

GC-MS analysis of oxysterols and their formation in cultivated liver cells (HepG2).

Oxysterols play a key role in many (patho)physiological processes and they are potential biomarkers for oxidative stress in several diseases. Here we developed a rapid gas chromatographic-mass spectrometry-based method for the separation and quantification of 11 biologically relevant oxysterols bearing hydroxy, epoxy, and dihydroxy groups. Efficient chromatographic separation (resolution≥ 1.9) was achieved using a medium polarity 35%-diphenyl/65%-dimethyl polysiloxane stationary phase material (30 m × 0.25 mm inner diameter and 0.25 μm film thickness). Based on thorough analysis of the fragmentation during electron ionization we developed a strategy to deduce structural information of the oxysterols. Optimized sample preparation includes (i) extraction with a mixture of n-hexane/iso-propanol, (ii) removal of cholesterol by solid phase extraction with unmodified silica, and (iii) trimethylsilylation. The method was successfully applied on the analysis of brain samples, showing consistent results with previous studies and a good intra- and interday precision of ≤20%. Finally, we used the method for the investigation of oxysterol formation during oxidative stress in HepG2 cells. Incubation with tert-butyl hydroperoxide led to a massive increase in free radical formed oxysterols (7-keto-chol> 7β-OH-chol>> 7α-OH-chol), while 24 h incubation with the glutathione peroxidase 4 inhibitor RSL3 showed no increase in oxidative stress based on the oxysterol pattern. Overall, the new method described here enables the robust analysis of a biologically meaningful pattern of oxysterols with high sensitivity and precision allowing us to gain new insights in the biological formation and role of oxysterols.

Polarized disinformation. The coverage of US presidential election by Polish TV

RESEARCH OBJECTIVE: Analysis of how the 2020 US presidential election was covered and framed by Polish television news programs, and whether the polarization of media and politics in Poland was reflected in the studied content, influencing its bias.
 THE RESEARCH PROBLEM AND METHODS: The analysis of the coverage of the US presidential campaign by three nationwide TV news programs – TVN, TVP and Polsat by using content analysis with elements of framing analysis and comparative analysis.
 THE PROCESS OF ARGUMENTATION: The article consists of four parts: the first explains the methodology of the study, the second discusses how presidential elections are covered and framed and what influences the national media being interested in covering foreign events. The third part presents the results of the study, and the last contains the discussion and conclusions.
 RESEARCH RESULTS: The coverage was dichotomous and there was a correlation between the political affiliation of the media and their choice of framing. The media used a combination of game, strategy and conflict framing that highlighted differences between Trump and Biden in terms of the election results and their personal attributes. We found that the electoral rivalry was portrayed as a conflict between the candidates and that the Polish media constructed “enemy” images of candidates and voters depending on their political sympathies.
 CONCLUSIONS, INNOVATIONS, AND RECOMMENDATIONS: The polarization of media and politics in Poland was reflected in the coverage of the US election. The broadcasters placed Polish political conflicts in the context of the US campaign. It shows that foreign events may be covered by national media through the prism of political bias.

The Representation of Public Opinion in Routine U.S. Network News

ABSTRACT Against a backdrop of increasing opinion polarization and distrust in mainstream news media, we investigate when and how U.S. evening newscasts represent citizen opinions. This paper focuses on the different public opinion displays presented in the news and the viewpoints they portray. Using a content analysis of 1,577 items from CBS, ABC, and NBC evening news, we find that public opinion is represented relatively more often in foreign and political news. Broad inferences to public opinion are most common in news coverage, followed by protests and vox pops. Lastly, we find that public opinion representation does not present notable viewpoint diversity.

Identification of aggregated 2D cobalt tellurides using a spatial self-phase modulation technique.

We report a previously unreported application of the spatial self-phase modulation (SSPM) technique for recognizing solute-solvent interaction in a suspension of 2D material. Broadband optical absorption of the 2D Co2Te3 leads to a nonlinear optical (NLO) susceptibility for the monolayer, i.e., χ M o n o(3) of 1.5 ×10-9 (3.3 ×10-9) esu at 532 (632) nm, which is 1-2 orders higher than for the 2D CoTe and CoTe2. The fine structure of the SSPM patterns is analyzed to explore the foundations of the observed NLO effects. With increasing polarity of the liquid media, a change of 2D Co2Te3 from homophonous dispersion to aggregation occurs, as confirmed from in situ optical microscopy and UV-vis absorption spectroscopy. As a result, type-I (thickest outer ring) SSPM ring patterns are converted to type-II (thinnest outer ring) SSPM ring patterns. Therefore, using SSPM with a CW laser as an optical tool to identify solvent-polarity-induced aggregation in 2D materials is possible.

Conformational dynamics modulating electron transfer.

Diffusional dynamics of the donor-acceptor distance are responsible for the appearance of a new time scale of diffusion over the distance of electronic tunneling in electron-transfer reactions. The distance dynamics compete with the medium polarization dynamics in the dynamics-controlled electron-transfer kinetics. The pre-exponential factor of the electron-transfer rate constant switches, at the crossover distance, between a distance-independent, dynamics-controlled plateau and exponential distance decay. The crossover between two regimes is controlled by an effective relaxation time slowed down by a factor exponentially depending on the variance of the donor-acceptor displacement. Flexible donor-acceptor complexes must show a greater tendency for dynamics-controlled electron transfer. Energy chains based on electron transport are best designed by placing the redox cofactors near the crossover distance.

Discovering Polarization Niches via Dense Subgraphs with Attractors and Repulsers

Detecting niches of polarization in social media is a first step towards deploying mitigation strategies and avoiding radicalization. In this paper, we model polarization niches as close-knit dense communities of users, which are under the influence of some well-known sources of misinformation, and isolated from authoritative information sources. Based on this intuition we define the problem of finding a subgraph that maximizes a combination of ( i ) density, ( ii ) proximity to a small set of nodes A (named Attractors ), and ( iii ) distance from another small set of nodes R (named Repulsers ). Deviating from the bulk of the literature on detecting polarization, we do not exploit text mining or sentiment analysis, nor we track the propagation of information: we only exploit the network structure and the background knowledge about the sets A and R , which are given as input. We build on recent algorithmic advances in supermodular maximization to provide an iterative greedy algorithm, dubbed Down in the Hollow (dith), that converges fast to a near-optimal solution. Thanks to a novel theoretical upper bound, we are able to equip dith with a practical device that allows to terminate as soon as a solution with a user-specified approximation factor is found, making our algorithm very efficient in practice. Our experiments on very large networks confirm that our algorithm always returns a solution with an approximation factor better or equal to the one specified by the user, and it is scalable. Our case-studies in polarized settings, confirm the usefulness of our algorithmic primitive in detecting polarization niches.

Medium electric field-induced ultrahigh polarization response and boosted energy-storage characteristics in BNT-based relaxor ferroelectric polycrystalline ceramics

Lead-free dielectric ceramics with a high recoverable energy-storage density (Wrec) and improved efficiency (η) are crucial for the development of pulse power capacitor devices. Although Wrec has been constantly improving, mainly via an increased breakdown electric field strength (Eb), a large driving electric field (>500 kV/cm) increases security risks and consequently increases insulating technology costs. In this work, we present a new (Bi0.5Na0.5)TiO3 (BNT)-based relaxor ferroelectric system, (1−x)(0.75Bi0.5Na0.4K0.1TiO3-0.25SrTiO3)-xBi(Mg0.5Ti0.5)O3 (BS-xBMT), with x ranging from 0.05 to 0.20. BMT disrupts both the A- and B-site long-range ferroelectric order of the ABO3 perovskite-structured BS matrix, induces polar nanoregions, and simultaneously increases Wrec and η. Aided by the viscous polymer process, the Eb with x = 0.15 increased to 270 kV/cm, and a maximum polarization (Pm) of 62 μC/cm2 was attained. A boosted Wrec of 4.82 J/cm3 and a high η of 84.9% were simultaneously obtained, together with good temperature stability from 30 to 140 °C. These results show that BNT-based dielectric ceramics with superior energy-storage properties can be obtained under a medium electric field.

Efficacy and safety of permeation enhancers: A kinetic evaluation approach and molecular mechanism study in the skin

This study sought to provide approach for evaluating and predicting the efficacy and safety of permeation enhancers on the basis of their kinetic distribution behavior in the skin dictated by physicochemical properties. Herein, the efficacy-safety regularity of eight permeation enhancers were studied with ex vivo skin permeation study, small-angle X-ray scattering, MTT assay, H&E staining, and in vivo skin erythema analysis, classifying into the following three categories: high enhancement–low irritation, medium enhancement–high irritation, and low enhancement–low irritation. These three modes were positively correlated with the distribution amount of permeation enhancers in the skin layers and verified by the in vitro tape-stripping study. The kinetic parameter, effective-safety index (IES), was proposed to describe the regularity of enhancement effect tendency and irritation risk, and the relationship between IES and physicochemical properties of permeation enhancers was analyzed with multiple regression analysis. According to the results of modulated temperature differential scanning calorimetry and dielectric spectrum, permeation enhancers with high lipophilicity and low polarity had IES > 1, suggesting high enhancement effect and low irritation due to their higher affinity with the stratum corneum (SC) than with epidermis (EP). Permeation enhancers with medium lipophilicity and medium polarity exhibited 0 < IES ≤ 1, showing medium enhancement effect and high irritation, as determined by their comparable affinity with the SC and epidermis (EP). However, permeation enhancers with low lipophilicity and high polarity had IES → 0, demonstrating low enhancement effect and irritation, as indicated by their poor affinity with the SC. In summary, different physicochemical properties of permeation enhancers influenced their affinities with skin layers, resulting in their different enhancement effect and irritation potential. This study will provide a theoretical basis and criteria for evaluating and predicting the safety and efficacy of permeation enhancers, which will enable a more rational selection of permeation enhancers in the optimization of transdermal patches.

An effective benzothiazole-indandione D-π-A fluorescent sensor for “ratiometric” detection of hydrazine: Its solvatochromism properties and applications in environmental samples and living cells

Hydrazine (N2H4) has high toxic impact and is widely used as raw material. As a result, it poses serious health risks and the following environmental pollution. Therefore, hydrazine's detecting techniques remains constantly under investigation. Herein, we report a ratiometric D-π-A fluorescent probe displaying NIR emission based on the ICT mechanism to detect N2H4. Other tested analytes have no observable interferences on the sensitivity and selectivity. The probe has sensitivity for N2H4 down to 1.29 μM with quick detection time (about 2.0 min). Moreover, the probe demonstrates solvatochromism with obvious emission varying from dull red to green, which implied high sensitivity to medium polarity. A portable smartphone platform for point-of-care detection of N2H4 in water samples is constructed. As a proof of real samples, the probe is successfully applied to sense N2H4 in water samples, to bioimage N2H4 in living cells and in plant cells with low cytotoxicity, suggesting significant potential application. This strategy opens up the preparation of new ratiometric fluorescence systems for bioimaging and environmental monitoring applications.

Thermally Activated Delayed Fluorescence: Polarity, Rigidity, and Disorder in Condensed Phases.

We present a detailed and comprehensive picture of the photophysics of thermally activated delayed fluorescence (TADF). The approach relies on a few-state model, parametrized ab initio on a prototypical TADF dye, that explicitly accounts for the nonadiabatic coupling between electrons and vibrational and conformational motion, crucial to properly address (reverse) intersystem crossing rates. The Onsager model is exploited to account for the medium polarity and polarizability, with careful consideration of the different time scales of relevant degrees of freedom. TADF photophysics is then quantitatively addressed in a coherent and exhaustive approach that accurately reproduces the complex temporal evolution of emission spectra in liquid solvents as well as in solid organic matrices. The different rigidity of the two environments is responsible for the appearance in matrices of important inhomogeneous broadening phenomena that are ascribed to the intertwined contribution from (quasi)static conformational and dielectric disorder.

Molecular simulations of the adsorption of aniline from waste-water

Molecular simulations of adsorption processes have received considerable attention. Despite the attention, exploration of the literature shows serious limitations, among which solvent and temperature effects are the most important. In this work, we propose a computational approach to study the adsorption of aniline (as an example of pollutant) from wastewater using coronene as adsorbent. We identified all possible adsorption sites using classical molecular dynamics for further optimization at the ωB97XD/aug-cc-pVDZ level of theory. Three different solvation schemes have been explored: implicit solvation of aniline + coronene, explicit solvation of aniline + coronene, and implicit-explicit solvation of aniline + coronene. For the explicit solvation, we used six water molecules, while the implicit solvation is performed using the PCM (polarizable continuum medium) solvation model. For each of the four cases (gas phase and the three solvation schemes), the adsorption free energy is evaluated as function of temperature from 200 K to 400 K. The results show that solvation has a considerable effects on the adsorption free energy. Furthermore, we noted that the adsorption free energy varies from −39.5 kJ mol−1 at 200 K to 27.7 kJ mol−1 at 400 K using the implicit-explicit solvation of aniline + coronene. This result highlights the importance of considering temperature effects in molecular simulations study of adsorption processes.

Inducing spin-order with an impurity: phase diagram of the magnetic Bose polaron

We investigate the formation of magnetic Bose polaron, an impurity atom dressed by spin-wave excitations, in a one-dimensional spinor Bose gas. Within an effective potential model, the impurity is strongly confined by the host excitations which can even overcome the impurity-medium repulsion leading to a self-localized quasi-particle state. The phase diagram of the attractive and self-bound repulsive magnetic polaron, repulsive non-magnetic (Fröhlich-type) polaron and impurity-medium phase-separation regimes is explored with respect to the Rabi-coupling between the spin components, spin–spin interactions and impurity-medium coupling. The residue of such magnetic polarons decreases substantially in both strong attractive and repulsive branches with strong impurity-spin interactions, illustrating significant dressing of the impurity. The impurity can be used to probe and maneuver the spin polarization of the magnetic medium while suppressing ferromagnetic spin–spin correlations. It is shown that mean-field theory fails as the spinor gas approaches immiscibility since the generated spin-wave excitations are prominent. Our findings illustrate that impurities can be utilized to generate controllable spin–spin correlations and magnetic polaron states which can be realized with current cold atom setups.

Solvent polarity influence on chemiexcitation efficiency of inter and intramolecular electron-transfer catalyzed chemiluminescence

The parameters which determine the efficiency of chemiluminescence, and bioluminescence transformations are a continuous matter of experimental and theoretical studies. In this sense, we report here a study of the solvent polarity influence on four Chemically Initiated Electron Exchange Luminescence (CIEEL) systems. Two of them comprise intermolecular CIEEL systems with low efficiency – catalyzed decomposition of diphenoyl peroxide and spiroadamantyl-1,2-dioxetanone; the other two are highly efficient in producing excited states – the peroxyoxalate reaction through an intermolecular CIEEL, and the induced decomposition of a phenoxy-substituted 1,2-dioxetane derivative via intramolecular CIEEL. These four CIEEL systems are studied in binary solvent mixtures with similar viscosity but different polarity, as measured by the empirical solvent polarity parameter ET(30). Reaction rate constants for all the systems increase with increasing polarity, indicating the occurrence of electron or charge transfer in the rate-limiting step of these transformations. For the intermolecular systems, singlet quantum yields generally rise with medium polarity to a maximum value and decrease for higher polarities. This agrees with stabilization of the radical ion pair intermediate by solvation at an optimal medium polarity. In contrast, higher polarity promotes the separation of these charged species, thereby avoiding electron back-transfer between radical ion pairs, essential for chemiexcitation. The singlet quantum yields in the intramolecular CIEEL system show a steady increase with the medium polarity, reaching values close to the maximum possible quantum yield of 1.0 E mol−1, indicating the importance of biradical ion stabilization and the occurrence of the whole reaction sequence in an intramolecular manner.

The Influence of the Medium Polarity on the Molecular Weight of Poly-2-hydroxyethyl Methacrylate

The Influence of the Medium Polarity on the Molecular Weight of Poly-2-hydroxyethyl Methacrylate

Through-Space Charge Transfer: A New Way to Develop a High-Performance Fluorescence Sensing Film towards Opto-Electronically Inert Alkanes.

New strategies are in high demand for fast, sensitive, selective, on-site and real-time detection of the important but challenging alkane vapors owing to their opto-electronic inertness. Herein, we report, for the first time, a high-performance fluorescent film sensor (FFS) for the alkanes with a rationally designed through-space charge transfer (TSCT) molecule as the sensing fluorophore. Steady-state fluorescence, femto-second transient absorption spectroscopy and theoretical studies revealed continuous TSCT dynamics in the excited U-shaped molecule with increasing medium polarity. Furthermore, the interlocked, face-to-face alignment between the donor and acceptor favors mass transport of the analyte molecules in the film state. As anticipated, the compound-based FFS showed an experimental detection limit of ≈10 ppm for n-pentane, less than 5 s for a full detection, negligible interference and super-stability, revealing the effectiveness of the design strategy. Notably, the sensor is small (≈3.7 cm3 ), power-saving, and workable at room temperature.

Through‐Space Charge Transfer: A New Way to Develop a High‐Performance Fluorescence Sensing Film towards Opto‐Electronically Inert Alkanes

AbstractNew strategies are in high demand for fast, sensitive, selective, on‐site and real‐time detection of the important but challenging alkane vapors owing to their opto‐electronic inertness. Herein, we report, for the first time, a high‐performance fluorescent film sensor (FFS) for the alkanes with a rationally designed through‐space charge transfer (TSCT) molecule as the sensing fluorophore. Steady‐state fluorescence, femto‐second transient absorption spectroscopy and theoretical studies revealed continuous TSCT dynamics in the excited U‐shaped molecule with increasing medium polarity. Furthermore, the interlocked, face‐to‐face alignment between the donor and acceptor favors mass transport of the analyte molecules in the film state. As anticipated, the compound‐based FFS showed an experimental detection limit of ≈10 ppm forn‐pentane, less than 5 s for a full detection, negligible interference and super‐stability, revealing the effectiveness of the design strategy. Notably, the sensor is small (≈3.7 cm3), power‐saving, and workable at room temperature.

Social media networks, fake news, and polarization

We study how the structure of social media networks and the presence of fake news affects the degree of misinformation and polarization in a society. For that, we analyze a dynamic model of opinion exchange in which individuals have imperfect information about the true state of the world and exhibit bounded rationality. Key to the analysis is the presence of internet bots: agents in the network that spread fake news (e.g., a constant flow of biased information). We characterize how agents’ opinions evolve over time and evaluate the determinants of long-run misinformation and polarization in the network. To that end, we construct a synthetic network calibrated to Twitter and simulate the information exchange process over a long horizon to quantify the bots’ ability to spread fake news. A key insight is that significant misinformation and polarization arise in networks in which only 15% of agents believe fake news to be true, indicating that network externality effects are quantitatively important. Higher bot centrality typically increases polarization and lowers misinformation. When one bot is more influential than the other (asymmetric centrality), polarization is reduced but misinformation grows, as opinions become closer the more influential bot’s preferred point. Finally, we show that threshold rules tend to reduce polarization and misinformation. This is because, as long as agents also have access to unbiased sources of information, threshold rules actually limit the influence of bots.

Caffeine metastable zone width and induction time in anti-solvent crystallization

In this study, the anti-solvent approach was used to investigate caffeine's induction time and metastable zone width (MSZW). Chloroform is used as a solvent, and carbon tetrachloride is used as an anti-solvent. Initially, caffeine solubility data is gathered in the chloroform/carbon tetrachloride mixture at various chloroform mass fractions. Caffeine solutions with various concentrations were then created to determine the MSZW. The anti-solvent (carbon tetrachloride) was injected into the solution to achieve supersaturation. The metastable zone limit was obtained by adding the anti-solvent at a constant rate and using turbidity changes in the system. The time of induction in various supersaturations was also investigated. In this section, various concentrations of solutions were created. Then, the system was instantly supersaturated with an anti-solvent. The period between the addition of the anti-solvent and the change in the turbidity of the solution was known as the induction time. The visual technique is compared to the use of an online turbidimeter before starting induction time measurements, and it is shown that the induction times obtained with the online turbidimeter are shorter and more accurate. Additionally, the induction time was investigated by various supersaturations, and it was discovered that as the supersaturation approaches the metastable zone border, the induction time decreases. Furthermore, in the same supersaturations, the influence of mixing on induction time was explored, and it was revealed that the higher the stirring speed, the shorter the induction time. Finally, the interfacial energy of solid–liquid phase was calculated for two systems with different initial chloroform mass fractions. It was shown that a reduction in polarity of medium increases the interfacial energy.

Online polarization and cross-fertilization in multi-cleavage societies: the case of Spain

The impact of the social media (SM) has been seen on the one hand as the cause of large exacerbation of negative messages, responsible for massively harmful societal phenomenon against democracies. On the other hand, recent studies have begun to look at how these online channels were able to provide a new impulse in human communication. The novelty of our work resides on analysing several axes of polarizations related to different societal topics. We believe our approach to reflect a more complex society, differing from the recent literature, which has considered a unique left–right dichotomic cleavage. Our methodology consists of extracting topics from the priority themes of the SM debate, using BERT language processing techniques and TF-IDF model. Our results show situation of social media interactions in a multidimensional space does exist. We highlight how social media behaviours, polarization and cross-fertilization differ as upon concrete topics. We argue therefore the ‘mega-identity partisanship’ which differentiate US online users in two different spaces cannot be extended for the rest of countries taking as first evidence the case of Spain. Further research should extend our conclusions for a possible generalization.

Not "My" crisis: Social identity and followers' crisis responses to COVID-19.

Operationalizing social group identification as political partisanship, we examine followers’ (i.e., US residents’) affective experiences and behavioral responses during the initial COVID‐19 outbreak in the United States (March to May 2020). In Study 1, we conducted content analyses on major news outlets’ coverage of COVID‐19 (N = 4319) to examine media polarization and how it plays a role in shaping followers’ perceptions of the pandemic and leadership. News outlets trusted by Republicans portrayed US President Donald Trump as more effective, conveyed a stronger sense of certainty with less negative affective tone, and had a lower emphasis on COVID‐19 prevention compared to outlets trusted by Democrats. We then conducted a field survey study (Study 2; N = 214) and found that Republicans perceived Trump as more effective, experienced higher positive affect, and engaged in less COVID‐19 preventive behavior compared to Democrats. Using a longitudinal survey design in Study 3 (N = 251), we examined how emotional responses evolved in parallel with the pandemic and found further support for Study 2 findings. Collectively, our findings provide insight into the process of leadership from a social identity perspective during times of crisis, illustrating how social identity can inhibit mobilization of united efforts. The findings have implications for leadership of subgroup divides in different organizational and crisis contexts.